Asynchronous Motor Nameplate Recognition, Identical-Name Terminal Identification, and Star-Delta Connection Conversion of Windings

Hands-on Motor Repair - Insulation and Protection Specifications

The nameplate of an electric motor is the basis for recognizing and servicing the motor. As shown in Table 16-1, nameplate parameters include model number, rated power, rated voltage, rated current, insulation class, connection method, and protection class.

Table 16-1 Nameplates for three-phase asynchronous motors
Electromagnetic brake three-phase asynchronous motors
Model	YEJ112M-4	serial number	0243
rating	4kW	rated voltage	380 V
rated current	8.9A	connection	△
excitation voltage	170V	rated speed	1440r/min
noises	LW 79 dB(A)	braking torque	40N-m
protection class	IP44	rated frequency	50 Hz
Weight	56kg	Standard number	JB/T 6456-92
work system	S1	Insulation class	Class B insulation
date of manufacture		August 2000

1. Models:The model number reflects the basic features of the motor, including product code, specification code, special environment code, etc. For example: Y100L1-2, Y stands for asynchronous motor, 100 stands for seat center height, L stands for seat length, 1 stands for core length and 2 stands for pole number. For example: Y100L1-2, Y stands for asynchronous motor, 100 stands for the center height of the seat, L stands for the length of the seat, 1 stands for the length of the iron core, and 2 stands for the number of poles; YR stands for wire-wound motor, YB stands for explosion-proof motor, YD stands for speed-regulating motor, YQ stands for high starting torque motor, YZ stands for lifting and metallurgical motor, and YH stands for marine motor, etc. When choosing a motor, you should choose the right model according to the situation. When selecting a motor, choose the appropriate model according to the situation. When replacing motors, try to replace them with the same model.

2. Rated power Pɴ:The rated power is the mechanical power output from the shaft when the motor is operated under rated conditions.

3. Rated voltage U and rated frequency f:Rated voltage and rated frequency refer to the line voltage and its frequency applied to the stator windings of the motor when the motor is operated under rated conditions, e.g. 380 V, 50 Hz; 440 V, 60 Hz, respectively.

4. Rated current I:The rated current is the line current on the stator windings of the motor when the motor is operated under rated conditions.

5. Rated speed n:Rated speed is the number of revolutions per minute of the motor when the motor is operated under rated conditions.

6. Wiring patterns:The wiring method refers to the connection method of the motor winding when the motor is operated under rated conditions, and there are two types: △ and Y.

7. Insulation class:The insulation class is the maximum temperature allowed for the motor as determined by the insulation material. The maximum temperatures permitted for materials of different insulation classes are shown in Table 16-2.

Table 16-2 Insulation Material Temperature Ratings
hierarchy	A	E	B	F	H
最高允许温度	105℃	120℃	130℃	155℃	180℃

8. 防护等级：防护等级是指电动机的防尘、防水等级，用 IPXX 表示。

(1) 第一个数：防尘等级 (0~6级)
0级：无防护；1级：防直径>50 mm 的固体；2级：防直径>12mm 的固体；3级：防直径>2.5mm 的固体；4级：防直径>1mm 的固体；5级：防尘；6级：尘密。

(2) 第二个数：防水等级 (0~8级)
0级：无防护；1级：防滴；2级：15°防滴(垂直方向)；3级：防淋水(60°防滴)；4级：防溅；5级：防冲水；6级：防猛烈海浪；7级：防浸水；8级：防潜水。
如 IP44 表示4级防尘4级防水。

9. 工作制 (运行方式)：
S1:连续运行，电动机在额定条件下可长时间运行。
S2:短时运行，电动机在额定条件下只能工作规定的时间，可分为：15min、30 min、60 min、90 min 四种。
S3:断续周期工作制。

10. 标准编号：标准编号是指制造这台电动机所依据的标准，其中，GB 为国家标准，JB 为部标准。

二、定子绕组首尾端 (同名端) 的判别

(一) 通电感应法

1. 理相：先用万用表电阻挡测量任意两绕组端头之间的电阻，若测量得到的电阻比较小，则此两端头属于同一相绕组。用同样方法判断其余两相绕组，并做好标记。

2. 接线、判断 (见图16-1)：
(1) 在通电瞬间：若万用表指针正偏，则U₁、W₁ 为同名端。
(2) 用同样方法判断U₁、V₁, 进而判断出三套绕组的极性。

图16-1 通电感应法测试同名端

(二) 绕组串联法

1. 理相：方法同通电感应法。

2. 接线、判断 (见图16-2)：
在第一相绕组上通上低压(3～36 V) 交流电，用万用表分别测量第二相电压U₂5、第三相 U₃6,以及两相绕组串联后的总电压Us₆。
(1)若Us₆=U₂₅+U36, 则2、6为同名端。
(2)若U₆=U₂₅-U36, 则2、3为同名端。

图16-2 绕组串联法测试同名端

(三) 剩磁感应法

1. 理相：方法同通电感应法。

2. 接线、判断 (见图16-3)：
转动转子：
(1) 若万用表指针不摆动或摆动最小，则 1、2、3 为同名端。
(2) 若万用表指针摆动比较大，则 1、2、3 不全是同名端，应该交换任意一相两个线头，再试验。若万用表指针不摆动或摆动最小，则交换正确，判断结束；若万用表指针仍然摆动比较大，则应交换另外一相再试，直到万用表指针不摆动或摆动最小为止。

图16-3 剩磁感应法测试同名端

三、绕组的星三角连接转换

定子绕组是三相电动机的电路部分，三相电动机的三相定子绕组由三个彼此独立的绕组组成，每个绕组又由若干线圈连接而成。每个绕组即为一相，每个绕组在空间相差120°电角度。每相绕组有两个引出端，一个为首端，另一个为尾端。三相绕组共有六个引出端，分别引到机座接线盒内的接线柱上，首端分别标为 $U_1$、$V_1$、$W_1$, 末端分别标为 $U_2$、$V_2$、$W_2$。这六个引出端在接线盒里的排列如图16-4所示，通过改变接线柱间连接片的连接关系，可以接成星形或三角形。

图16-4 三相定子绕组的接线方式